Mike Royce, Beckett’s former mentor returned last night on Castle! For those who had forgotten, in Royce’s last episode, he turned out to be a dirty cop that took bribes and impeded Beckett’s progress on a case. She was also in love with him, so his betrayal was especially harsh. Royce drags himself across pavement while an ominous man stalks him with a gun and a silencer. The man shoots Royce.

Jump ahead to the crime scene: Captain Montgomery looks grim, Castle looks unsure and Beckett just looks sad. No one wants Beckett to see Royce’s body, but she’s made of tougher stuff and she wants closure. Lanie gives Beckett the details: shot in the leg, crawled away, got shot. Beckett tells them that, last she heard, Royce moved to LA after he lost his bounty hunter license. Lanie finds one more thing: a letter in Royce’s pocket addressed to Beckett.

Ryan and Esposito find the murder weapon--a cheap, throw-away gun with traces of an expensive silencer in threads on the barrel. Castle asks the question we’re all thinking: why a cheap gun and an expensive silencer? Because the killer followed Royce from LA. He couldn’t take his gun on the plane, but silencers are harmless by themselves. The crew runs flights from LA to New York to find anything suspicious. Their first his: Neal McCauley (yes, like DiNiro’s character in “Heat”), a man with a fake driver’s license, no credit score who bought his ticket at the airport an hour before the flight. The only hiccup? McCauley (or whoever he is) flew back to LA two hours after Royce was shot.

Montgomery is understandably hesitant about sending Castle and Beckett to LA, but this is a TV show and I’m sensing a destination episode, so he’ll cave in roughly five minutes. Montgomery wants to get more evidence and bump it over to the LAPD. Kate is not having any of that nonsense, but she covers it well. She’s just going to take some vacation days, okay? No big deal. Maybe she’s going to go see the Hollywood sign. Whatever. Fans of Law and Order: SVU will recognize this tactic, because Benson and Stabler each do this twice a season. The next shot is Kate on a plane. The flight attendant tells her she’s been upgraded to first class... by Castle. Beckett warns Castle that she’s not a cop in LA, so they have to fly under the radar. Castle’s version of under the radar is a bright red sporty convertible and a two bedroom suite in a fancy hotel.

Beckett and Castle go to the address on Royce’s driver’s license and come face to face with... Gene Simmons. From Kiss. Gene proceeds to hit on Beckett, which she deftly deflects. Gene was letting Royce stay in his guest house. Apparently Royce was in the business of helping people--sort of like Angel, except not a vampire (and presumably less broody). Gene has the headshot of an actress who Royce helped earlier--a woman named Violet. Beckett calls her talent.

Meanwhile, back in New York, Ryan and Esposito find security camera footage of the front of the building where Royce was shot. They can’t see the shooter’s face or the license plate, but they can tell that he’s white and that the driver of the car is black. Esposito has a friend at TSA. Ryan suggests hitting him up for footage of the security checkpoint. If he was wearing the same clothes at the airport as he was after the shooting, they might be able to see his face.

In LA: Violet is shooting a commercial at the same studio where they’re shooting Heat Wave. Castle gets waylaid by the producer of Heat Wave while Beckett looks for Violet... who didn’t show up for work that day. New York: Esposito and Lanie make kissy faces at each other, but they stop as soon as Lanie discovers that the bullets are dissolving.

Beckett and Castle break into Violet’s house, where they discover a piece of paper with Royce’s flight number written on it, surveillance photos, strange articles about corgis, surfing and wine tasting. They get busted by Detective Seeger, the LA, male version of Beckett. Seeger has Montgomery on the phone. The Captain sounds a lot like an angry dad, if an angry dad could threaten to fire you. This doesn’t scare Beckett. Instead, she calls Ryan to make him look for Violet. He agrees, of course.

Esposito picks up the phone to deliver the news: they have a photo of the killer, courtesy of TSA. Fans of Prison Break will recognize the killer as Lincoln Burrows! Lincoln, so nice to see you again! Castle, using his magical internet searching capabilities, discovers that the man in Violet’s surveillance photos is Charles Kelvin, head of Kelvin North America (an R&D facility). Kelvin’s hobbies? Wine tasting, corgis and surfing, just like the articles Violet had. She was researching Kelvin, but why?

They find Kelvin at the beach, during his “surf hour.” Kelvin went on a date with Violet. Castle plays a tape recording of Kelvin’s voice--the words, strung together, make up a vocal key to his offices. Violet taped her conversation with Kelvin and coaxed the right words out of him. Kelvin rushes back to the office, where he discovers that all of his prototypes have been stolen... prototypes of dissolving bullets.

New York: Ryan hasn’t found Violet, but he did find an ex-boyfriend of hers who saw her alive and let her stay the night. She was gone the next morning, and in her wake came an African-American guy who beat up Violet’s ex, looking for her. Ryan got the guy to a sketch artist (presumably after he got him to a hospital), so the killer’s driver has a face.

Beckett and Castle share a sweet moment as Beckett starts to allow herself to mourn for Royce. There’s an almost-kiss, but Beckett just retreats into her room. Hesitantly, she returns to the main room, but Castle has already gone into his room. The moment has passed.

The next morning, Beckett is hard at work on a murder board, courtesy of the concierge. Beckett has worked out a time-line of the heist, including which guard the thieves would have to pass--a man named Reggie Walsh who asked to be reassigned the next day. A knock: it’s Seeger! He wants to know why they were poking around in the Kelvin robbery case. Beckett heads him off and makes him leave. What they need to do, she says, is question the guard, Reggie Walsh. She’s not a cop in LA, but he doesn’t need to know that.

Jump to the actors who are playing Raley and Ochoa (the Ryan and Esposito to Beckett’s Nikki Heat), in a police cruiser, with Beckett and, I can only assume, Reggie Walsh in the back seat. Beckett covers his head with her jacket (to hide him from the reporters, she says) and takes him to Zenith Studios. Walsh tells Beckett that two men came to him and offered him 500 dollars to take a cigarette break at midnight. His description matches the sketch and photo Beckett has of the killer and his driver, and to top it off, Walsh heard the driver call the killer Ganz. Back in New York, Ryan runs a search that reveals the killer as Russell Ganz, a high profile, violent thief. He also runs a search on known-associates, which turns up Donald Mannis--the driver hunting Violet.

Ganz lives large and well, so Castle taps into the network of people who cater to the rich and powerful: the concierge. Maurice tells Castle and Beckett that Ganz is at a poolside cabana, surrounded by beautiful woman. So Beckett pulls on a bathing suit (one-piece, very nice ABC), to show Ganz that there’s one beautiful woman he hasn’t met yet. She introduces herself as Lola Black and coyly pretends to be a fence for a Colombian drug cartel. Beckett pushes Ganz too hard (to keep him from seeing Castle), and blows her cover. Castle, however, was just taking a picture of Ganz’s recent call list.

Back in New York, Montgomery sees straight through Ryan and Esposito’s lies, but gives them his blessing to find Violet and help Beckett put the case to rest. In LA, Beckett calls Seeger for help. They track Mannis’ number to Manhattan. Beckett wants to call Mannis and tell them that Ganz is cutting him out of the deal, pushing him to call Ganz while they listen in. Seeger gets a warrant started.

In New York, Ryan and Esposito have found Violet. While they’re getting into the car to take Violet back to the station, a man’s phone rings--it’s Mannis and he has a gun. He starts firing. Ryan pushes Violet to the ground, Esposito shoots Mannis and answers his phone. Esposito pressures Mannis to tell them where and when the deal is going down: Santa Monica Pier, at 6 pm. Castle points out that it’s 5:45 already. Anyone who has ever been to LA knows that unless you’re within a 15 minute walk to the Santa Monica Pier, there’s no way you’ll get there during rush hour. But they make it!

A huge, scary tattooed man walks around with a briefcase. He looks completely out of place at the amusement park on the pier. Seeger takes down the buyer while Beckett handles a man in the van nearby. Beckett chases Ganz down the beach. She shoots him once. Ganz says Royce told him that hell would rain down on him, but he never imagined hell would look like her. Beckett doesn’t kill him--she lets the LA cops take over and arrest him. She got her closure and they go home.

On the plane, Beckett reads the letter Royce left her. He tells her that she and Castle have something real, but that she shouldn’t let the job get in the way of her life. He warns her that the last thing she wants is to end her life thinking “if only.” With two episodes left in this season, I long to see how they resolve this Castle/Beckett tension!